DESCRIPTION: This is an application to continue support in years 4-8 for studies aimed at defining the mechanisms by which the molecular chaperone, GroEL, can assist the folding of denatured proteins. All of the research is to elucidate elementary steps of a single cycle of chaperonin facilitated protein folding. Many different experimental techniques are proposed ranging from site directed mutagenesis to X-ray crystallography and neutron scattering. The use of surface plasmon resonance is well used in these experiments. The proposed research would test 3 specific aims: 1) evaluate predictions of a model for GroEL function based on nucleotide promoted release of polypeptide chains. For example, the use of single-ring variants of GroEL would test the prediction that the ring with bound polypeptide binds nucleotides weakly, but promotes rapid non-native chain release. Further, it will be determined whether full nucleotide occupancy of a single ring is required for release of non-native chains. Methods would include hydrodynamic and scattering studies to determine nucleotide promoted conformational changes and whether they are concerted and follow saturation with nucleotide.